Two dimensional arrays of visible light emitting devices, such as light emitting diodes (LEDs), are becoming very useful in displays for portable electronic devices, such as telephones, cellular telephones, two-way radios, pagers, etc. Generally, these two dimensional arrays include large numbers of light emitting devices, from 5000 to 80,000 or more, with a specific example being 144 rows by 240 columns. An array the size of this specific example requires a total of 384 external interconnections to properly scan, or activate, to produce an image thereon.
A major problem facing the productizing of such arrays is the penalty paid for this very large number of connection, or bond, pads required to provide information to the array. The foremost drawback is the increased semiconductor die area required for the bond pads and interconnect fanout to connect the bond pads to the rows and columns. A significant portion of the projected cost of the semiconductor chip on which the array is constructed is in the starting material and, with the 144.times.240 example set up for wire bonded external interconnects, the emitting region (light emitting diode array) occupies less than 20% of the total die area with the remaining 80% required for bond pads and interconnect fan out. Direct chip attach (DCA) bonding will improve this ratio only slightly because of the larger pad sizes and interconnect pitches associated with the current state-of-the-art.
A larger bonding substrate area is also required since a similar pad and interconnect fanout pattern must be repeated on accompanying semiconductor chips containing the drive electronics. Furthermore, the drive chips themselves must be large to accommodate the large number of bond pads (384 in this example). The net result is a large overall module which is not attractive for the applications of portable electronic devices where a premium is placed on small physical volumes.
Therefore, it is highly desirable to achieve improved interconnect apparatus and methods of fabricating the improved interconnect apparatus.
It is a purpose of the present invention to provide new and improved integrated circuitry for driving large arrays of semiconductor devices.
It is a further purpose of the present invention to provide new and improved integrated circuitry which requires less semiconductor chip area for larger arrays of devices.
It is another purpose of the present invention to provide new and improved integrated circuitry which is relatively easy to fabricate and use.
It is another purpose of the present invention to provide new and improved integrated circuitry with new and improved arrays of light emitting devices.
It is still another purpose of the present invention to provide new and improved electro-optic integrated circuitry which is small enough to be conveniently used in portable electronic equipment.